Outer trim parts for automobiles, made of polymeric materials, are commonly colored by painting after the molding thereof. Although it is known that polymeric materials can be colored by blending pigments or dyes therein, realizing coloring conditions equivalent to the colored appearance and texture exhibited by painted metal materials for use in, for example, automobiles is so difficult that, as mentioned above, the automobile outer trim parts are painted after the molding thereof.
However, there is a problem such that the yield in painting step is low because of product deformation attributed to heat applied at the painting or because of painting irregularity to thereby result in a poor productivity. There is another problem such that a wide space is required for drying the paint to thereby render a layout of production line for automobile outer trim parts difficult. There is a further problem such that the conventional painting uses volatile toxic solvents, so that not only is work environment deteriorated but also a waste liquid treatment is to be coped with.
Methods of producing colored automobile outer trim parts, which realize the same appearance and texture as those of the conventional painted automobile outer trim parts composed of polymeric materials without the need to conduct painting, have recently been proposed with a view toward improving work environment and attaining cost reduction.
For example, a technique of coloring the surface of an automobile outer trim into a colored condition similar to that of the painted item with the use of a polymer film is introduced on page 48 of PLASTICS WORLD, July, 1996. The polymer film introduced thereon has a three-layer structure comprising a polyvinyl fluoride film and, sequentially laminated thereto, an acrylic resin layer and a pigment containing polyester layer.
However, the use of this polymer film encounters a problem such that high cost is inevitable because of the use of expensive fluoropolymer and acrylic resin, and also involves the danger that an interlayer separation would occur because of the lamination of different types of materials whose bonding is difficult. Moreover, this polymer film includes an easily hydrolyzable polyester, so that, when exposed to the weather or used in outer trim parts of automobiles driven on the beach or riverbed, the polyester layer reacts with water to thereby deteriorate and, hence, cause the danger of discoloration or peeling.
With respect to the recovery and recycling of automobile outer trim parts at the time of scrapping of automobiles, the above polymer film is a laminate of different types of materials, so that a material classification and collection of classified material are inevitable to thereby rather cause high cost. Thus, even if this polymer film is intended to be incinerated, the problem is encountered that a hazardous gas would be generated at the time of the incineration.
Apart from the above three-layer structured polymer film, it is also known to ploy a three-layer film comprising a surface layer of an acrylic polymer or fluoropolymer, a colored layer of a vinyl chloride polymer and a layer of a polypropylene or polyvinylidene fluoride which is easily bonded to a substrate.
However, being similar to the above mentioned polymer film, this three-layer film is a laminate of different types of materials and employs expensive fluoropolymer and acrylic resin, so that the use of the three-layer film encounters the same problems as experienced by the above mentioned polymer film.
Therefore, there is a demand for the development of a method of molding an automobile outer trim part which can be recycled and incinerated, and which exhibits the same colored appearance and texture as those of the painted part, irrespective of the avoidance of painting step, while exhibiting durability in water and which is fundamentally composed only of polymer. Further, there is a demand for the development of a laminated film or sheet for use in the molding method and an automobile outer trim part.